Stator of dynamo-electric machine

Abstract: A stator of a dynamo-electric machine includes core pieces (11) obtained by laminating iron plates divided in a circumferential direction per pole-tooth unit and having projecting and recessed engaging parts (14a,14b) at their dividing faces (13), and then welding the iron plates by laser at their inner and outer peripheries, and a winding part (16) formed around each pole-tooth unit of the core pieces, wherein a predetermined number of the core pieces are bonded into a shape of a loop with the projecting and recessed engaging parts engaged with each other and rigidly welded in outer peripheries of bonding faces by laser in a laminating direction.

Description: The present invention relates to a method of making a stator, and to a stator of a dynamo-electric machine (referred to as a motor hereinafter) used mainly in industrial equipment. High-density of windings and space-saving at the ends of windings are increasingly important to realize compact and highly efficient motors. Particularly, in order to catch up with the recent tide of high-speed operation, space-saving, and high output characteristics of a robot, it is necessary to use magnets of high magnetic flux density for a rotor of a servo motor of the robot and to increase the winding density of a stator. Although inserted windings have conventionally been practiced to achieve high density of winding, the technique has a demerit that a large space is consumed at the endsof the windings. Nowadays, therefore, the stator is constructed in most cases in such a manner that a core is divided and the winding is wound in alignment outside the stator, thereby to achieve windings with high density and saving of space at the endsof the windings. The constitution of a conventional stator will be described first below. Fig. 3 indicates the constitution of a stator in a first conventional example intended for high-density winding and saving of space at an end of the winding. In Fig. 3, reference numerals respectively represent: 21 a first core constituting the outside of a core; 22 a second core constituting the inside of the core; 23 a joint part connecting pole-tooth units of the second core 22 adjacent to each other; 24 an insulator; 25 a winding part; and 26 a resin part. In the above constitution, the winding part 25 is wound in alignment outside the stator with high density orthogonally to the insulator 24. A predetermined number of winding parts 25 are inserted into each pole-tooth unit of the second core 22. The second core 22 is then inserted in the inner periphery of the first core 21, thereby constituting a stator core. A stator is hence perfected in the integrated structure when the resin part 26 is formed. Figs. 4 and 5 show the constitution of a stator in a second conventional example. In the representative example of the stator in Figs. 4 and 5, the outer periphery of a layered core is divided in the direction of an output shaft. In Fig. 4, the layered core 31 is divided half by a dividing face 32. Reference numeral 33 denotes a winding part, and reference numeral 34 of Fig. 5 denotes a resin part. In the constitution as above, the winding part 33 has a winding orthogonal to the outer periphery of the layered divided core 31. The divided parts of the core 31 are brought to butt against the dividing face 32 and integrated by means of the resin part 34. The constitution of the first conventional example has disadvantages as follows: 1) Since the core constituting the stator is divided at the outer periphery of the pole-tooth units, the joint part 23 connecting the pole-tooth units at the radial inner peripheries is necessitated to constitute and maintain the second core 22. 2) The magnetism leaks between the pole-tooth units at the joint part 23, with lowering the efficiency of the motor. Therefore, it is required to make the joint part 23 as thin as possible. 3) Although it is necessary to provide the resin part 26 so as to secure the rigidity in the above constitution of the stator, an insulation coating of the winding part 25 may be damaged when the resin part 26 is formed, thereby causing shortcircuiting between wires. 4) In accordance with the increase in size of the core, the pressing and forming plant of the core becomes large in scale, which results in the deterioration of the production efficiency. According to the constitution of the second conventional example, since the winding part 33 is wound at right angles to the outer periphery of the layered core 31, the winding part 33 cannot be aligned and occupies the winding space merely by 52-55%. Although space is saved at the end parts of of the windings, the winding parts project outward in the radial direction, thereby to increase the dimensions of the stator as a whole. From GB-A-13 02 093, a stator for a dynamo-electric machine is known which has a segmented form in which the winding part are pre-wound on bobbins which are then placed on pole-tooth units of the segmented core pieces. From JP-A-5030690 it is known to weld the stacked iron plates of the poles at their outer peripheries before the windings are wound the holes. It is an object of the present invention to provide a method of making a stator, as well as a stator itself for a dynamo-electric machine, in which the windings can be wound in alignment outside the stator with high density, and in which the end parts of the windings occupy less space. A joint part of the hole-tooth units which could decrease the magnetic efficiency of the dynamo-electric machine should be unnecessary, and also resin moldings to secure the rigidity should not be necessary. The stator should be designed in divided structure so that even a press plant of a small size could manufacture a large-size core for the stator. According to the invention, a method of making a stator of a dynamo-electric machine comprises the steps: a) forming a plurality of core pieces by, for each core piece, laminating a plurality of pole-tooth unit iron plates having projecting and recessed engaging parts at dividing faces thereof and inner and outer peripheries in a laminating direction and then welding said iron plates together by laser at said inner and outer peripheries, thereby forming the plurality of core pieces having respective pole-tooth units; b) forming a winding part around each of said pole-tooth units of said core pieces through a wire winding process; and c) laser-welding said core pieces together in the direction of lamination at outer peripheral bonding areas of said core pieces, with said projecting and recessed engaging parts engaged with each other and with said core pieces formed into an annular shape so as to form a rigid structure. In another aspect of the invention, a stator of a dynamo-electric machine comprises: a plurality of core pieces each having pole-tooth units, dividing faces, projecting and recessed engaging parts at said dividing faces and inner and outer peripheries, and each of said core pieces comprising a plurality of laminated iron plates that are laminated in a laminating direction and laser-welded together at said inner and outer peripheries, and winding parts wound around respective said pole-tooth units of said core pieces, wherein said plurality of core pieces form a rigid annular shape with said projecting and recessed engaging parts at said dividing faces engaging each other and said plurality of core pieces being laser-welded together with a weld extending in the laminating direction at said outer periphery. Preferable embodiments are defined in the dependent claims. These features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: Fig. 1 is a sectional plan view of a complete piece of a layered core divided per pole-tooth unit according to one embodiment of the present invention; Fig. 2 is a sectional plan view of a stator having the divided pieces of the core bonded into the shape of a loop; Fig. 3 is a sectional plan view of a stator in a first conventional example; Fig. 4 is a perspective view indicative of the appearance of a stator before sealed with the use of a resin in a second conventional example; and Fig. 5 is a side sectional view of the stator of Fig. 4. Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. A preferred embodiment of the present invention will be described with reference to the corresponding drawings. Fig. 1 shows a completed piece of a layered core divided per pole-tooth unit and Fig. 2 is a completed stator of a motor composed of a predetermined number of the completed pieces bonded annularly. The constitution of each of the above completed core piece and stator will now be discussed hereinbelow. Referring to Fig. 1, a core piece 11 is obtained by layering core iron plates divided per pole-tooth unit 11b and bonding the plates by laser at 12 on inner and outer peripheral surfaces 11d, 11e so as to integrally connect the plates with each other. The core piece 11 has projecting and recessed engaging parts 14a and 14b formed on the dividing faces 13 at its outer part 11c. An insulating part 15 is formed at the pole-tooth unit 11b of the core piece 11 and is prevented from removal by projections 11a. A winding part 16 is formed on the insulating part 15 around the pole-tooth unit 11b. A predetermined number of core pieces 11 are bonded one another at bonding areas 17 into the shape of a loop with the projecting and recessed engaging parts 14a and 14b engaged with each other as shown in Fig. 2. In the stator of the above-depicted constitution, the core pieces 11 are layered per pole-tooth unit 11b by punching the iron plates in a small-size press plant and then bonding the plates by laser at the welding parts 12. Thereafter, the insulating part 15 is formed at the pole-tooth unit 11b and then the winding part 16 is constituted in alignment with high density by an external winding machine. Thereafter, a predetermined number of core pieces 11 are formed into the shape of a circular cylinder by fitting the engaging parts 14a and 14b at the dividing faces 13, and then, the outer peripheral parts of the dividing faces 13 are rigidly welded by laser in the laminating direction to form the bonding parts 17. Accordingly, the stator is integrated with the required rigidity. The pole-tooth unit is formed in T-shape as shown in Fig. 1. The unit can also be formed in L-shape. The above-described arrangement according to the present invention displays the following operations. 1) Since the core is divided per pole-tooth unit 11b, a wire is wound in alignment for every piece of the core outside the stator at right angles to the pole-tooth unit 11b with high density (occupying ratio of the conductor is 70%). Therefore, the stator becomes compact and space-saving at the end part of the winding. 2) A projecting or recessed engaging part 14a, 14b is provided in the circumferential direction of each dividing face. After a predetermined number of core pieces 11 are combined into the shape of a circular cylinder by fitting the engaging parts, the outer peripheries 11e of the core pieces are welded in the layer direction. Accordingly in this constitution, it is prevented that the laser enters the winding part and burns the winding at the welding time. The welding is restricted to a small range, so that the effective length of the yoke is secured to maximum. Moreover, because of the rigidity of the stator being ensured, the resin molding becomes unnecessary and shortcircuiting is prevented. Further, since a joint part for the pole-tooth units is not required to constitute and maintain the core, the 5-10% deterioration of the efficiency of the motor due to the joint part is prevented. 3) Since the core is divided per pole-tooth unit 11b, the poles become thin, enabling the production of large-size cores even in a small press plant. Accordingly, the production efficiency is greatly improved.

Claims: A method of making a stator of a dynamo-electric machine comprising the steps of: a) forming a plurality of core pieces (11) by, for each core piece (11), laminating a plurality of pole-tooth unit iron plates having projecting and recessed engaging parts (14a, 14b) at dividing faces (13) thereof and inner and outer peripheries (11d, 11e) in a laminating direction and then welding (at 12) said iron plates together by laser at said inner and outer peripheries (11d, 11e), thereby forming the plurality of core pieces (11) having respective pole-tooth units (11b); b) forming a winding part (16) around each of said pole-tooth units (11b) of said core pieces (11) through a wire winding process; and c) laser-welding said core pieces (11) together in the direction of lamination at outer peripheral bonding areas (17) of said core pieces (11), with said projecting and recessed engaging parts (14a, 14b) engaged with each other and with said core pieces (11) formed into an annular shape so as to form a rigid structure. The method as claimed in claim 1, and further comprising the step of providing an insulating part (15) on each said core piece (11) before the winding part forming step b). A stator of a dynamo-electric machine, comprising: a plurality of core pieces (11) each having pole-tooth units (11b), dividing faces (13), projecting and recessed engaging parts (14a, 14b) at said dividing faces (13) and inner and outer peripheries (11d, 11e), and each of said core pieces (11) comprising a plurality of laminated iron plates that are laminated in a laminating direction and laser-welded together at said inner and outer peripheries (11d, 11e); and winding parts (16) wound around respective said pole-tooth units (11b) of said core pieces (11); wherein said plurality of core pieces (11) form a rigid annular shape with said projecting and recessed engaging parts (14a, 14b) at said dividing faces (13) engaging each other and said plurality of core pieces (11) being laser-welded together with a weld (17) extending in the laminating direction at said outer periphery (11e). The stator as claimed in claim 3, further comprising an insulating part (15) located between each of said pole-tooth units (11b) and each of said winding parts (16). The stator as claimed in claim 3 or 4, wherein each said core piece (11) has an outer part (11c) connected with said pole-tooth unit (11b) thereof, said projecting and recessed engaging parts (14a, 14b) and said dividing faces (13) being located on said outer part (11c). The stator as claimed in claim 5, wherein each said weld (17) extending in the laminating direction is located on said outer parts (11c) of two of said core pieces (11) so as to connect said core pieces (11) together. The stator as claimed in any of claims 3-6, wherein each of said core pieces (11) has a projection (11a) for preventing the winding part (16) from removing from the core piece (11).

Inventors: HIRANO MIKIO, KINASHI YOSHIKAZU, TAKEUCHI MANABU, WADA YUKITOSHI, HIRANO, MIKIO, KINASHI, YOSHIKAZU, TAKEUCHI, MANABU, WADA, YUKITOSHI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: H02K1
IPC codes: H02K1, H02K15